Error when accessing Site pages > Participants

We experienced this on moodle.org:

1. Log in to moodle.org as an ordinary user
2. Go to your dashboard or profile page and expand Site pages then click the link Participants i.e. https://moodle.org/user/index.php?id=1
3. Observe error 'Sorry, but you do not currently have permissions to do that (View participants)'

Expected result:
Participants link is not shown to users who do not have the appropriate permission

To reproduce this on any aite, you just need to set "Default frontpage role" to "Student" (like we have on moodle.org) rather than "Authenticated user of front page" (like we have on all other sites where we can't see it happening).
The reason for this misbehaviour is a bug in lib/navigationlib.php